Fuse



A. J. BOWIE FUSE fia/H5 2 massif/70N Sept. 28, 1943.

Patented Sept. 28, 1943 UNITED kSTATES PATENT OFFICE .FUSE

Augustus Jesse Bowie, San Francisco, Calif. Application August 4, 1940, serial No. 351,341

'z Claims.y (o1. 20o- 131) This invention applies particularly to high-tension fuses and fuse tubes f the unfilled type. It is customary in these tubes to provide a fuse near one end of the tube and a conducting link of very flexible copper strand to convey the current from this fuse to the terminal at the other end of the fuse. Often this link is fastened on the outside of the ferrule which contacts with the clip. When fuses of this kind blow, the fuse link is expelled from the tube and generally hangs down. A superior type of construction, however, is one wherein the lower end of the flexible link is connected to a compression type of cap which makes contact with the lower ferrule and when fuse blows, this cap and fuse link are both ejected Y from the tube. With this preferred construction, a pressure must be built up Within the tube and before the lower cap is expelled. With long tubes of small bore, when a fuse blows the heated air near the fuse is driven violently outward compressing the air surrounding the link and in some cases may cause this link to wad up within the tube and tend partially to seal it.

It is, of course, essential to eject this link from the tube and in order to accomplish this in the best fashion, it is advisable to have the ejecting means subjected to a material amount of pressure for an appreciable time.y With the end sealing cap, the pressure is applied only While the cap is being ejected from the ferrule, or a relatively short distance. In order` to overcome these difficulties, I make a greater part of the fuse lead of copper wire or of a fairly rigid strand which will not wad up by the rush of air before the end cap releases. Also, I make the ejected element subject to air pressure over a considerable period in order to give it the necessary velocity for proper ejection of the fuse.

Figure 1 shows a longitudinal section of the fuse tube and element.

Figure 2 shows the cross section thereof on the line AA.

Figure 3 shows an elevation of the fuse element only together with the fuse cap.

Figure 4 shows the lower end of the fuse element with an alternate construction.

Fig. 5 shows the lower end of a fuse element No. 6 is an insulating tube attached to 5 and containing the fuse element 1.

No. 8 is a filling material for generating pressure when the fuse blows.

No. 9 is a plug for sealing item 6.

No. I0 is preferably a solid copper link for conveying current from the fuse to ther other end of the tubeand attached to the fuse element byl sleeve II.

No. I2 is a compression type cap with thin walls and is provided with contact screw I3. This cap makes a light compression contact with the ferrule 3.

No. I4 is a combination connection sleeve and piston to one end of which the fuse lead is attached and to the other end the fiexible conductor I5 is attached; this lead being connected to cap I2 through the screw I3.

Nos. IG-IB are spacer collars preferably of light insulating material which are threaded loosely on the flexible conductor I5. The fuse wire 'I is taken through the terminal 5 to which it is soldered on the outside after passing through hole I'I.

Figure 4 is an alternate arrangement of the lower part of Figure l wherein the collars I6, I6 are omitted.

The actionof the fuse is as follows:

When the fuse I melts the heat generated thereby exerts pressure inside of the fuse tube which may or may not, as desired, be increased by the explosive medium 8. This generates high pressure within the tube causing the expansion of air to exert pressure on the cap I2. Owing to the stiffness of the fuse conductor I0, this will allow the rush of gases past it to react on the piston I4. As this fits fairly closely in the inner bore of the tube, the greater part of the pressure will be exerted on the end of piston I4 reacting on collars I6, IB and causing the cap I2 to be expelled. From the fact that I4 is an appreciable distance from the end of the tube, it will be subject to internal pressure only While it is being ejected from the tube thus giving the required pressure to eject the element I0 from the tube. If desired, the elements I6, I6 may be omitted as is shown in Figure 4. Thus the initial rush of gas from the heat generated by the blowing of the fuse is transmitted directly to piston I4 and the amount of energy for ejection of the fuse link I0 is determined by the distance of insertion of piston I4 Within the tube. This causes the fuse to act without crumpling of the element I0 and gives the desired velocity to the internal element which is to be ejected.

An added feature of these fuses is the fact that if the fuse blows violently it will melt the fuse wire from the opening Il thus opening a top vent. Furthermore, if this is not sufficient vent, the disc 5 is made so thin that it will be ejected from the hole in the nut 4, being drawn into a cup shape thus providing two safety factors for the upper end of the fuse which will prevent the blowing up of the fuse tube under pressures which would otherwise destroy it. V

Figure 5 shows in longitudinal section the lower end of the tube whereconnections are desired on the outside. In this case the element I4 is placed midway in the tube, and the element lll which may be either a solid wire or a stranded wire or if desired, may be of flexible wire. In this event the plunger I f1 will act positively to withdraw element IG from the fuse.

Having described my invention, what I claim is:

1. A high-tension fuse comprising a fuse tube, end terminals thereon, a fuse element located adjacent to one end terminal7 a lead connecting said fuse element to the second end terminal, and a piston element mounted on said lead and adapted to be ejected together with said lead through `pressure caused by the blowing of said fuse, said piston acting through a material length of travel within said tube.

2. A fuseas in claim l and one or more collars between'said piston andsaid second terminal, 4and a sealing member adapted rto seal said tube to the atmosphere and to be expelled from said second terminal through pressure transmitted from said piston through the collars to said sealing member.

3. A fuse tube comprising an insulating tube,

and containing ferrules on each end, a fusible element near one end ferrule and connected through a lead to the ferrule on the opposing end, said fusible element being connected to its adjacent ferrule through a disc which is provided with an orifice normally closed by said fusible element, said orifice being open to the .air upon fusing of said fusible element providing a safety valve for the fuse tube 4., A fuse as in claim 3.said disc being rigidly secured in place but adapted to be expelled as a cup if the pressure within said fuse tube exceeds a pre-determined amount.

5. A fuse as described in claim 1 in which said lead comprises a fairly rigid portion connected to said fuse element and a relatively short flexible portion connecting said rigid portion to said second end terminal.

6. A fuse as described in claim 1 and including a sealing member forming a portion of the electrical circuit. between said lead and said second end terminal and adapted to be expelled when `struck by said pistento break the electrical circuit at saidsecondend terminal.

A'7. A -fuse asdescribed in claim 1 and including a sealing member forming a portion of the electrical circuit between said lead and said second end terminal and adapted to be expelled when struck by. said piston to break the electrical circuit at said second end terminal, said lead comprising a fairly rigid portion between said fuse element and said piston and a relatively short flexible .portion between said piston and .said sealing member.

AUGUSTUS JESSE BOWIE. 

